Hi Matthew,
I figured everyone else as weighed in on this I might as well too.
Doing it yourself is most certainly do-able. Give all your phones and laptops, a dhcp pool for visitors and so forth public v4 addresses, you'll meet the APNIC requirement easy enough.
My main suggestion is to consider your core business, is it building networks, or is it delivering a service over a network. It's easy for us geeks to get carried away with building awesome technical solutions, but what are the business benefits? sometimes there aren't many. Just a good excuse to buy plenty of nice toys.
Perhaps there is an inter-tubes provider of some kind around you could approach to tailor a solution, you can provide your requirements to them (such as their core must be diverse physically and logically, their access to you must be physically diverse. Their hand-overs to upstream must be equally as diverse... If they can't explain why their network is the best fit for your high availability requirements move to the next one.�
Its very possible you would get a better solution, also cheaper by working with an existing ISP.
Good luck.